Schito G C, Botta G A
Chemioterapia. 1987 Jun;6(3):174-8.
Patients admitted to intensive care units are extremely susceptible to infection due to hospital acquired pathogens. One of the most important reasons for the occurrence of infection is attributable to the fact that these patients are exposed to several prosthetic devices for diagnostic or therapeutic procedures. From this point of view the problem of prostheses-associated infection is presently of major concern in hospital acquired infection since the number of artificial polymers implanted in the human body is rapidly increasing in many medical fields. Several types of plastic and metal prostheses are utilized for medical purposes and they greatly differ in tissue compatibility. Only recently some information has been obtained about their susceptibility to bacterial adhesion and colonization. The thermodynamic approach considers hydrophobicity, or surface free energy, as the major factor in facilitating bacterial attachment, but probably this approach is inherently too simplistic and does not consider important factors such as conditioning films bathing the surface of the polymer. Moreover, in this model bacteria are considered as individual cells, but the available body of evidence indicates that cells form aggregates embedded in a matrix sticking to the surface. This sessile mode of growth, as opposed to that of free living cells (planktonic) has profound effect on growth, shape, metabolism of attached bacteria influencing sensitivity to antibiotic, disinfectants and to cellular and humoral host defenses. Adherent bacteria cannot be easily ingested by polymorphonuclear neutrophils (PMNs) which are rendered ineffective by aspecific activation upon contact with several polymers. All these factors contribute to make these infections chronic and cryptic by posing difficult diagnostic and therapeutical problems.
入住重症监护病房的患者极易受到医院获得性病原体的感染。感染发生的最重要原因之一是这些患者因诊断或治疗程序而接触多种假体装置。从这一角度来看，假体相关感染问题目前是医院获得性感染中的主要关注点，因为在许多医学领域，植入人体的人工聚合物数量正在迅速增加。几种类型的塑料和金属假体被用于医疗目的，它们在组织相容性方面有很大差异。直到最近才获得了一些关于它们对细菌黏附和定植敏感性的信息。热力学方法将疏水性或表面自由能视为促进细菌附着的主要因素，但这种方法可能本质上过于简单，没有考虑到诸如覆盖聚合物表面的调理膜等重要因素。此外，在这个模型中，细菌被视为单个细胞，但现有证据表明，细胞会形成嵌入黏附在表面的基质中的聚集体。这种固着生长模式与自由生活细胞（浮游）的生长模式相反，对附着细菌的生长、形状、代谢有深远影响，进而影响其对抗生素、消毒剂以及细胞和体液宿主防御的敏感性。黏附的细菌不容易被多形核中性粒细胞（PMN）吞噬，多形核中性粒细胞在与几种聚合物接触时会因非特异性激活而失效。所有这些因素通过带来诊断和治疗难题，导致这些感染成为慢性和隐匿性感染。
